[1.7.1] UUID error replacing local file with file external

   I have a local file in a WC. I have svn-deleted the local file and
re-added it as a file external from elsewhere (to the same WC location using
the immediate parent's svn:externals).

   However, on update I now get an error along the lines of:

Updating 'tools':

Fetching external item into 'tools/mksrn.pl':
svn: warning: W170009: Repository UUID
'a16ec33f-10fa-4864-f3e0-c4d0f3191a87' doesn't match expected UUID
'fc8517da-9189-6699-81a6-a7dc70dab01f'

At revision 499.
svn: E205011: Failure occurred processing one or more externals definitions

   [expected UUID is the local repo, the other is the remote one]

   Annoyingly I tried to re-create this with a dummy/example pair of repos,
and it all worked swimmingly.

   Any ideas as to how I can fix my WC? I'm not scared of a little (but I
do mean little) SQL ...

NB - real work done via TortoiseSVN on Windows, [working] test attempted on
Linux. Update error text above copied from Linux attempt to do same update
on broken WC.

-- 
[neil_at_fnx ~]# rm -f .signature
[neil_at_fnx ~]# ls -l .signature
ls: .signature: No such file or directory
[neil_at_fnx ~]# exit